We use the perfective will have when we are looking back from a point in time when something will have happened.

By the end of the decade scientists will have discovered a cure for influenza.
I will phone at six o’clock. He will have got home by then.

or looking "back" from the present:

Look at the time. The match will have started.
It’s half past five. Dad will have finished work.

We use would have as the past tense form of will have:

I phoned at six o’clock. I knew he would have got home by then.
It was half past five. Dad would have finished work.

We use would have in past conditionals to talk about something that did not happen:

If it had been a little warmer we would have gone for a swim.
He would have been very angry if he had seen you.
 

Exercise

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Comments

Hello sir. I have just saw this sentence on an academic article and it got me a little bit confused. "The competitive pressure
may spur local firms to operate more efficiently and introduce new technologies earlier than would
otherwise have been the case."

Now my question is should have the sentence been The competitive pressure
may spur local firms to operate more efficiently and introduce new technologies earlier than would
otherwise be case.

I feel "otherwise it would have been the case" is a sentence about past, but here the author is talking about the future so the sentence should have been completed by " otherwise it would be the case"

Can you please enlighten me, when you have time?

Thank you so much.

Hello M.Kemal,

Using 'be' in this sentence is also correct, but 'have been' is not wrong. Rather than referring to the past here, one can understand it as referring to an imaginary or hypothetical time, i.e. the time that would exist if the competitive pressure did not exist.

All the best,
Kirk
The LearnEnglish Team

hello sir
Can we say: "If it WAS a little warmer we would have gone for a swim.
He would have been very angry if he SAW you."
If we cannot. why?
Thank you.

Hello mohammad bazzy,

Yes, those forms are correct. Some people prefer 'were' instead of 'was' in second conditional sentences such as these, but 'was' is also commonly used with first and third person singular subjects.

All the best,
Kirk
The LearnEnglish Team

Hi! greetings & good-day!
I would like to know the difference between these two sentences. I think both of them have same assumption i.e by the end of the decade research will be finished. I am little bit confused!! please help me. Thanks.

1. By the end of the decade scientists will discover a cure for cancer
2. By the end of the decade scientists will have discovered a cure for cancer

Hello sudhir31,

The difference is more a difference of emphasis than anything. In 2, the fact that the cure has already been discovered is emphasised more than in 1, but that's about it. Although both sentences are fine, I'd say that 2 is more common and would encourage you to use it because the future perfect is very often used with expressions like 'by the end of ...'.

All the best,
Kirk
The LearnEnglish Team

Sir, I would like to ask if this sentence is correct or not and why?
Question: Honey, have you had your dinner? Answer: Yes I...(what)?

Hello Roweena,

Yes, the question is grammatically correct. Our short forms page explains what short form of the verb should be used in the answer. Please tell us what you think it is if you have any doubts and we can confirm if you've got it right or not.

All the best,
Kirk
The LearnEnglish Team

Hi,
could you explain why it is used "would have pp" in the following paragraph,
The students who go to study abroad and are able to send messages home with no difficulty, while in the past they would have had to buy stamps and go to the post office.

It is said that "would have pp" should use when we want to talk about something that did not happen in the past, but in this paragraph it actually happened. So I am a little bit confused!!!

Hi Maryam606,

The reason the form 'would have had to' is used here is because the speaker is describing a hypothetical past situation. The condition is not stated, but we can add it to make the meaning clear:

The students who go to study abroad and are able to send messages home with no difficulty, while if they had been in the same situation in the past they would have had to buy stamps and go to the post office.

If the sentence described real students in the past then the form would be different:

The students who go to study abroad now are able to send messages home with no difficulty. On the other hand, students in the past had to buy stamps and go to the post office.

 

Best wishes,

Peter

The LearnEnglish Team

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